Lossless nonlinear analog gain controller in image sensor and manufacturing method thereof

Abstract

An image sensor comprises an active pixel sensor (APS) array, a first analog-to-digital converter (ADC), and a ramp signal generator. The APS array has includes a plurality of pixels of arranged in a second order two-dimensional matrix, and wherein the APS array generates a reset signal and an image signal for each pixel of selected columns. The first ADC has includes correlated double sampling (CDS) circuits for each column of the APS array, and wherein the first ADC generates a digital code corresponding to the difference between the reset signal and the image signal using an output ramp signal that is applied to the CDS circuits for each column. The ramp generator generates the output ramp signal in which a low illumination portion and a high illumination portion have different slopes.

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATION

[0001] This application claims priority to Korean Patent Application No. 10-2005-0078046, filed on Aug. 24, 2005, the disclosure of which is herein incorporated by reference in its entirety. BACKGROUND OF THE INVENTION

[0002] 1. Technical Field

[0003] The present disclosure relates to an image sensor and, more particularly, to a lossless non-linear analog gain controller in a CMOS image sensor (CIS) type image sensor.

[0004] 2. Discussion of Related Art

[0005] CMOS image sensors are commonly used in portable cameras, digital still cameras, web cameras and the like to convert an image into a digital signal. The digital image signal that is output from the CMOS image sensor contains red, green, and blue image data. The digital image signal is processed to drive a display device such as a liquid crystal display.

[0006] A CMOS image sensor uses a correlated double sampling (CDS) method and uses a ramp signal to generate a digital signal from...

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